trans-Dichloridobis[(S)-(−)-1-(4-methylphenyl)ethylamine-κN]palladium(II)

The molecular PdII title complex exhibits a square-planar coordination about the central metal atom, provided by two trans-arranged chlorido ligands and two nitrogen atoms from the two neutral organic ligands.


Structure description
The chemistry of Pd II compounds with diverse ligands represents a rich area within organometallic chemistry, extensively explored in organic synthesis (Hartwig, 1998;Mu ¨ller & Beller, 1998).Pd II compounds also exhibit cytotoxic activity, which makes them interesting for certain therapeutic applications.Moreover, Pd II compounds with amine ligands have a central role in catalytic conversions due to the hydrogen bond developed between the amino group and the catalyst.In the presence of excess amine, 16-electron PdCl 2 L 2 (L = amine) adducts, usually existing as a mixture of cis and trans isomers, emerge as viable starting materials for cyclopalladations (Ryabov, 1990;Cattalini & Martelli, 1969).While monodentate Pd II -amine complexes tend to display general instability as reaction intermediates, bis(amine)-Pd II complexes have garnered substantial attention for their involvement as intermediates in amination reactions (Widenhoefer & Buchwald, 1996;Seligson & Trogler, 1991).In this context, our focus has shifted towards complexes derived from optically pure chiral amines.We present here the molecular and crystal structures of trans-dichlorido bis[(S)-(À )-1-[(4-methylphenyl)ethylamine]palladium(II).
The asymmetric unit comprises a single molecule, as shown in Fig. 1.The molecular complex adopts a square-planar metal coordination environment around the central Pd II A view of the crystal packing shows that individual molecules are organized into supramolecular ribbons defined by C-H� � �Cl and N-H� � �Cl hydrogen bonding interactions (Table 1); the ribbons extend parallel to [100] (Fig. 2).The cohesion between the ribbons is accomplished mainly by weak van der Waals interactions (Steiner, 1996;Desiraju, 1996).The Pd� � �Pd separations between neighboring Pd II complexes vary from 5.5027 (5) to 6.5385 (5) A ˚, indicating that there is no strong interaction among these metal atoms.

Synthesis and crystallization
A solution of bis(benzonitrile)palladium(II) chloride (0.66 g, 0.17 mmol) in CH 2 Cl 2 (5 ml) was added to a solution of ( S

Figure 2
The crystal packing of the title complex in a projection along [100].The dashed lines indicate intermolecular hydrogen bonds.All H atoms that are not involved in these interactions have been omitted for clarity; displacement ellipsoids are drawn at the 50% probability level.

Figure 1
The molecular structure of the title complex with displacement ellipsoids drawn at the 50% probability level.
filtered off, dissolved in DMF, and the solution was slowly evaporated.After a few days, orange crystals were collected.Yield 23%.

Special details
Geometry.All esds (except the esd in the dihedral angle between two l.s.planes) are estimated using the full covariance matrix.The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry.An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s.planes.Refinement.The hydrogen atoms attached to carbon and nitrogen atoms were positioned with idealized geometry and constrained to ride on their parent atoms, and were refined isotropically using a riding model.
atom.There are slight distortions from the ideal square-planar geometry, as revealed by a deviation of 0.025 A ˚of the Pd II atom from the plane defined by atoms Cl2, N2, Cl1, N1.The interatomic distances from the central Pd II atom to the ligand atoms are 2.039 (4) A ˚[Pd1-N1] and 2.053 (4) A ˚[Pd1-N2]; the average Pd-Cl bond length is 2.298 A ˚.The pairs of Cl and amine ligands are trans-aligned around the central Pd II atom and characterized by a Cl1-Pd1-Cl2 angle of 177.22 (6) � and an N1-Pd1-N2 angle of 179.39 (18) � ; the Cl1-Pd1-N1 angle amounts to 88.25 (12) � , with other angles approximately 90 � .The sp 3 hybridization of the N atoms and the C9 and C17 atoms cause the non-planarity of the molecular structure.The amine ligands are arranged differently around the central Pd II atom.The Cl1-Pd1-N1--N2-C17.Both amine ligands exhibit a gauche conformation, as revealed by the torsion angle C17-N2-N1-C1 = À 55.6 (4) � .

Table 2
Experimental details.